Hyponitrous acid, H2N202, was first obtained in the form of its salts by E.

Hantzsch (Ann., 1896, 2 9 2, pp. 34 0 et seq.) hyponitrous acid and nitramide are to be regarded as stereoisomers, being the anti-and synforms of the same compound.

Hyponitrous acid is formed by passing nitrous fumes into its methyl alcohol solution.

A typical member is nitric oxide; carbon monoxide and nitrous oxide may also be put in this class, but it must be remembered that these oxides may be regarded, in some measure at least, as the anhydrides of formic and hyponitrous acid, although, at the same time, it is impossible to obtain these acids by simple hydration of these oxides.